More than a dozen women’s rights activists have been targeted since May. Most campaigned for the right to drive and an end to the Kingdom’s male guardianship system, which requires women to obtain the consent of a male relative for major decisions.

Government spokesmen did not immediately respond to a request for comment on the latest reports.

Badawi received the United States’ International Women of Courage Award in 2012 for challenging the guardianship system, and was among the first women who signed a petition calling on the government to allow women to drive, vote and run in local elections.

Al-Sadah, from the Shia-majority Qatif province, has also campaigned to abolish the guardianship system and the right to drive.

“The arrests of Samar Badawi and Nassima Al-Sadah signal that the Saudi authorities see any peaceful dissent, whether past or present, as a threat to their autocratic rule,” said Sarah Leah Whitson, Middle East director at Human Rights Watch, in a statement.

“Saudi authorities have targeted and harassed Badawi for years. In addition to her advocacy for women’s equality, she has campaigned energetically for both her former husband and her brother to be released from prison,” the statement added.

Badawi’s former husband is already in prison, serving a 15-year sentence for human rights activism, and her brother Raif Badawi, a prominent blogger, is serving a ten-year sentence for expressing controversial opinions online.